在 TikZ 树中标记非叶边

Question

在用 TikZ 制作的树中，我想标记树的边缘。我在 StackExchange 上看到了使用的示例edge from parent node{label}，但这似乎只适用于树的最后一条边缘，一直延伸到叶子。下面是我所指的一个例子（图片下方的代码）。

首先，我在 TikZ 中创建树并用 标记边edge from parent node{...}，这对于连接到叶子的边很有效：

B但是，如果我尝试做同样的事情来标记和之间的边缘BB，则会发生以下情况：

以下是代码：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{trees}
\begin{document}
\begin{tikzpicture}[level distance=1.5cm,
    level 1/.style={sibling distance=6cm},
    level 2/.style={sibling distance=3cm},
    level 3/.style={sibling distance=1.5cm},
    edge from parent/.style={draw}]
  \node{$\bullet$}
  child {node {\texttt{B}} 
    child {node{\texttt{BB}}
      child {node{\texttt{BBB}} edge from parent node[left]{$\frac{3}{4}$}}
      child {node{\texttt{BBG}}}
    }
    child {node{\texttt{BG}}
      child {node{\texttt{BGB}}}
      child {node{\texttt{BGG}}}
    }
  }
  child {node {\texttt{G}}
    child {node{\texttt{GB}}
      child {node{\texttt{GBB}}}
      child {node{\texttt{GBG}}}
    }
    child {node{\texttt{GG}}
      child {node{\texttt{GGB}}}
      child {node{\texttt{GGG}}}
    }
  };
\end{tikzpicture}

\begin{tikzpicture}[level distance=1.5cm,
    level 1/.style={sibling distance=6cm},
    level 2/.style={sibling distance=3cm},
    level 3/.style={sibling distance=1.5cm},
    edge from parent/.style={draw}]
  \node{$\bullet$}
  child {node {\texttt{B}} 
    child {node{\texttt{BB}} edge from parent node[left]{$\frac{2}{3}$}
      child {node{\texttt{BBB}} edge from parent node[left]{$\frac{3}{4}$}}
      child {node{\texttt{BBG}}}
    }
    child {node{\texttt{BG}}
      child {node{\texttt{BGB}}}
      child {node{\texttt{BGG}}}
    }
  }
  child {node {\texttt{G}}
    child {node{\texttt{GB}}
      child {node{\texttt{GBB}}}
      child {node{\texttt{GBG}}}
    }
    child {node{\texttt{GG}}
      child {node{\texttt{GGB}}}
      child {node{\texttt{GGG}}}
    }
  };
\end{tikzpicture}
\end{document}

Answer 1

必须edge from parent node在所有子节点后添加：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{trees}
\begin{document}
\begin{tikzpicture}[level distance=1.5cm,
    level 1/.style={sibling distance=6cm},
    level 2/.style={sibling distance=3cm},
    level 3/.style={sibling distance=1.5cm},
    edge from parent/.style={draw}]
  \node{$\bullet$}
  child {node {\texttt{B}} 
    child {node{\texttt{BB}}
      child {node{\texttt{BBB}}
        edge from parent node[left]{$\frac{3}{4}$}
      }
      child {node{\texttt{BBG}}}
      edge from parent node[left,xshift=-4pt]{$\frac{2}{3}$}%<- moved
    }
    child {node{\texttt{BG}}
      child {node{\texttt{BGB}}}
      child {node{\texttt{BGG}}}
    }
  }
  child {node {\texttt{G}}
    child {node{\texttt{GB}}
      child {node{\texttt{GBB}}}
      child {node{\texttt{GBG}}}
    }
    child {node{\texttt{GG}}
      child {node{\texttt{GGB}}}
      child {node{\texttt{GGG}}}
    }
  };
\end{tikzpicture}
\end{document}